1. Field of the Invention
This invention relates generally to techniques for maintaining the position of read/write heads in alignment with tracks of data stored on magnetic media, such as disk drives and magnetic tape drives. In particular the present invention relates to a servo controlled, magnetic head positioning system.
2. Description of the Prior Art
In a conventional magnetic tape drive system, multiple read/write head groups are generally mounted within a carriage and used to perform read/write operations on magnetic media, particularly magnetic recording media such as magnetic tape. The drive system typically includes a positioning mechanism, such as a stepper motor, that moves the carriage to position the heads with respect to the tape. The stepper motor receives position instructions from the system processor using servo data from the tape read by a magnetic head, particularly a magnetic recording head such as a tape head.
The accuracy and repeatability of tape head positioning and tracking with respect to the tape is a critical factor in the operation of such drive systems. One common problem is AC offset, that is, AC head to tape misalignment. In addition, motion of the magnetic tape itself perpendicular to the normal direction of tape motion, called "tape wander", contributes to this problem. The conventional limits of such accuracy and repeatability of positioning and tracking are some of the major limiting factors in ongoing developments of tape drive systems with increased accuracy and data density.
What is needed is a head positioning and tracking technique with greater accuracy and repeatability than is conventionally available, particularly with respect to the ability to compensate for AC offset of the head with respect to a data track and with respect to track perpendicular tape wander.